This invention relates to an airflow shield between a cab and a trailer of a semi-trailer truck to improve airflow around the vehicle and, more particularly, to a flexible shield which allows pivotable movement between the tractor and the trailer while closing the gap therebetween and which also provides a roof extension which automatically raises as the trailer mounts the fifth wheel to permit the trailer to be connected to the tractor. The two piece construction of the roof extension also allows it to adapt to variations in trailer heights.
The semi-trailer truck, as used for hauling cargo over the highway, has advantages over the conventional truck in that it can carry a much larger cargo and also is more adaptable for steering the truck in close quarters. One disadvantage, however, is that there is a gap between the tractor and trailer which will increase the aerodynamic drag of the tractor-trailer combination compared to a straight truck having a body of the same frontal area as the trailer.
Another of the disadvantages caused by the gap between the tractor and trailer is that air turbulence and uneven air pressures occurring along the sides of the trailer accentuate the tendency of a trailer to yaw and add to the difficulty of steering and handling the combination on the highways.
U.S. Pat. No. 3,711,146 shows a device which streamlines a tractor-trailer by completely closing the gap to reduce the aerodynamic drag. However, the device itself is not very streamlined.
U.S. Pat. No. 4,750,772 also shows a streamlining device on a tractor-trailer combination which has rigid extenders for the sides and a roof fairing which extend into the gap as far as possible without interfering with normal trailer movement relative to the tractor and including a small elastomeric section to prevent damage to the trailer and/or extenders if the trailer should articulate excessively. These extenders do not close the gap but only minimize it.
U.S. Pat. No. 2,101,793 teaches a side extenders which close the gap and are spring loaded to contact the front of the trailer through rollers. U.S. Pat. No. 4,397,496 teaches similar extenders but made of flexible materials. However, the trailers in both patents have a round front end which is not very practical from a cargo space standpoint and has been largely discarded by the trailer industry. Rectangular trailer fronts will not accommodate spring loaded extenders and flexible extenders of more than a few inches will tend to bend under the aerodynamic forces encountered by a tractor-trailer at highway speeds especially in cross winds.